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How to Tell Who's Tracking You Online

A new tool reveals your virtual footsteps and who's taking note

Mozilla has introduced Collusion, an add-on for the Firefox browser that shows you how companies are tracking you as you surf the Web. A cool visual demonstration of the software illustrates all the links that form as you crisscross just a few popular sites online, including IMDb, the New York Times and the Huffington Post. The software shows the connections among sites you visit and third-party tracking and advertising networks such as DoubleClick and Scorecard Research. It makes plain the invisible web that has been woven through the Web.

The software was created as a prototype by Atul Varma, who explained in a blog post that he “didn’t know a lot about tracking myself, so I whipped up a Firefox add-on called Collusion to help me visualize it better. The results were a little unsettling.”

Collusion will help you understand how you are being tracked online, but it won’t stop it from happening. For that, you can disable third-party cookies on your browser and install other add-ons such as TrackerBlock. A number of Internet giants have also announced support for a “do not track” button, although that option may not become available until the end of the year.


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This article was published in print as "How to Tell Who's Tracking You Online."

Michael Moyer is the editor in charge of physics and space coverage at Scientific American. Previously he spent eight years at Popular Science magazine, where he was the articles editor. He was awarded the 2005 American Institute of Physics Science Writing Award for his article "Journey to the 10th Dimension," and has appeared on CBS, ABC, CNN, Fox and the Discovery Channel. He studied physics at the University of California at Berkeley and at Columbia University.

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Scientific American Magazine Vol 306 Issue 5This article was originally published with the title “How to Tell Who's Tracking You Online” in Scientific American Magazine Vol. 306 No. 5 (), p. 0